I'd Rather Marry an Ancestral Tablet Than Be a Concubine: I Rule the Duke's Mansion

【Marriage Swap + Mansion Intrigue & Face-Slapping + Sisterly Contrast + Scumbag Couple's Crematorium】 My cousin and I were engaged at the same time. She was to marry the heir of the Duke's estate, while I was betrothed to the second son. Cousins marrying brothers—it was considered a beautiful story. But then the heir died on the battlefield, and the ducal title fell to the second son. To escape the stigma of being a "husband-killer," my cousin turned to my fiancé. On the eve of my wedding, my fiancé asked me to willingly become his concubine. 【Though it’s a bit unfair to you as a concubine, what more could a lone orphan girl like you want than to marry into the Duke’s estate? You...